Prime surface heat exchanger with dimpled sheets



Nov. 8, 1960 c:. s. SIMPELAAR 2,959,400

PRIME SURFACE HEAT EXCHANGER WITH DIMPLED SHEETS Filed Nov. 27, 1957 2 Sheets-Sheet 1 2 v INVENTOR:

cums s. SIMPELAAR Nov. 8, 1960 c. s. SIMPELAAR 2,959,400

PRIME SURFACE HEAT EXCHANGE-R wmx DIMPLED snmws Filed Nov. 27, 1957 2 Sheets-Sheet 2 Q 0 f /7 20 f 34 20 WQ ,1 5:3 36 /.3 a

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lNl/ENTOR: ClYDE S. SIMPELAAR A T TORNEV PRIlVIE SURFACE HEAT EXCHANGER WITH DIMPLED SHEETS Clyde S. Simpelaar, Racine, Wis., assignor to Modine Manufacturing Company, Racine, Wis., a corporation of Wisconsin Filed Nov. 27, 1957, Ser. No. 699,355

4 Claims. (Cl. 257-245) This invention relates to a prime surface heat exchanger with dimpled sheets.

A fundamental object of this invention is to provide a prime surface heat exchanger for high temperature and high pressure use, but with the excahnger light in weight as compared to heat exchangers of the same capacity. In expressing this object, by the term high pressure is meant pressure in excess of one hundred p.s.i., and of course, the term prime surface refers to an exchanger consisting primarily of plates and having no separate or additional internal members such as fins so that the exchanger is constructed of single sheets or plates each side of which is in contact with a different fluid, and heat transmission is solely and directly between the plates and the fluid. It is recognized that prime surface heat exchangers consisting primarily of plates with or without internal reinforcement are old in the art. These, however, have been constructed of materials of heavier gage than that required in the hereinafter described construction, or where lighter gauge materials are employed in the prior art exchangers, theyare suitable only for low pressures. Also, where the prior art exchangers have been constructed for the high pressures referred to, then internal supports are essential, and such internal supports or structures also serve as a secondary fin surface so that the exchanger is not then classed as a prime surface heat exchanger. It is further recognized that the provision of the dimples to serve as internal supports in a flat tube is old in the art, and dimpled sheets have been employed in oil regulator systems and air preheaters and the like.

Other objects of this invention include the provision of a heat exchanger which is efficient in its operation; holds the entrance losses to a minimum; can be readily redesigned for desired proportioning for flow volume and surface in each pass; provides, as an integral part of the exchanger, meansfor connecting headers and the like to the exchanger; and to provide an exchanger whose overall structure has an inherent ability to absorb stresses due to temperature changes and differentials, and to distribute these stresses throughout the structure without damage thereto. In accomplishing these objects, a heat exchanger with materials to gage dimension down to as low as .002 inch is provided with virtually all of the weight of the exchanger constituting effective heat transfer surface so that it can be expressed that 95% of the weight of the exchanger constitutes effective heat transfer surface. 7

' Fig. 1 is a perspective view of a heat exchanger showing one embodiment of this invention.

Fig. 2 is an enlarged sectional view of a fragment of the exchanger shown in Fig. 1 and taken on the line 2 2 of Fig. 1.

Fig. 5 is an elevational view of a fragment of the exchanger shown in Fig. 4 viewing the corner of Fig. 4, but also having the corner piece of Fig. 4removed.

Fig. 6 is a perspective view similar to Fig. 4 but showing a different cut-out on the exchanger corner, and

, showing a fragment of a connection.

Fig. 7 is a plan view of a fragment of two sheets of Fig. 6.

Fig. 8 is a plan view of Fig. 6 with the top plate removed.

Fig. 9 is a plan view similar to Fig. 8 but with a 7 different cut-out on the exchanger corner and with a different corner piece.

The drawings show the exchanger to consist of the top planular plate 10 and an identical bottom plate 11 with the four corners of the two plates cut out at locations indicated 12 such that the corners receive the shown Y-shaped corner pieces 13. The corner pieces 13 are shown to be formed of one continuous piece of stock with the formations such that the ends 14 and 16 of the corner pieces are preferably disposed at right angles while the intermediate section 17 is overlapped upon iteslf. It should thus be understood that the corner pieces 13 are bonded to the plates 11 by soldering or the like such that the bond exists along the lines 18 adjacent the corner ends 14 and 16 and also along the line 19 adjacent and around the intermediate portion 17 of the corner piece. With this arrangement, the corner pieces 13 and the plates 10 and 11 are well secured together in fluid tight relation along the bond line described. It will also be seen hereinafter that the heat exchanger plate or sheets are similarly bonded to the corner pieces 13 so that the pieces 13 are not only fluid tight with the plates 10 and 11 and the intermediate sheets, but the corner pieces are also physically well bonded to the plates and the sheets. At this itme, it should also be noticed that the corner pieces and the plates 10 and 11 present four box-like edges or sides of the exchanger, and this is particularly useful in welding or otherwise attaching header connections or the like to the exchanger with no requirement for intermediate connecting members, as the box-like sides of the exchanger are readily suitable for the connection mentioned.

Disposed intermediate the plates 10 and 11 and parallel thereto are sheets 20, 21, 22, and 23. See Figs. 2, 3 and 5. There is, of course, a plurality of sheets 21 andof sheets 22, and as shown in Fig. 3, the sheets are dimpled or indented with rows of large dimples 26 and smaller indentations or dimples 27, as viewed in Fig. 3. Of course, the dimples and indentations are not holes in the sheets, butare rather offsets or dimples as mentioned and are provided for the purposes mentioned hereinafter, and the opposite surface of the sheets has the protrusions formed by the dimples. The "sheets 21 are similarly:

21 and 22 to be joined together such that, as shown in.

Fig. 5, the edges 28 of the sheets 21 are directed angularly upwardly and are overturned and crimpedon the edges. 29 of the sheets 22 such that the two edges 28 and 29" are pressed together and can be fluid tightly bound by soldering or preferably by heating the exchanger to melt the coating metal on the sheets. Similarly, the edges 31 of the sheets 22 are bent upwardly and crimped over the edges 32 of the sheets 21. In this arrangement, the pairs of edges or sides 28, 29, 31, and 32 are joined so that they are staggered as viewed in Fig. 5. Thus, one

fiuid can enter one side of the exchanger while a different fluid enters the exchanger at the adjacent side to establish Patented ,Nov. 8., 1960 a cross flow of fluids which are completely separated from each other. Only the sheets 21 and 22 are disposed at the interior of the exchanger which is, therefore, light in weight as required, and the protrusions provide good heat tiansfer and necessary strength to the sheets for resisting iiiteinal pressure. With regard to the nineteen should be understood that the two sizes could vary to be equal or unequal, as desired, and thus the amount of flow through each pass can be controlled by the correspondingly variable pass volumes. Also, the dimples are shown staggered with respect to the two directions of cross flow and this provides for rnaxirnurn heat transfer between the passes as the fluids will be impinged against the staggered protrusions of e the dimples which leave the exchanger with straight-through passes of only a fraetiori of the total entrance openings. Of course, the dimples could also be located aligned rather than staggered. v

The protrusions are preferably flattened on their tops or crests, as shown, and this provides good surface contact for heat transfer and bonding, and the crests of the protrusions are in contact with each other. Fig. 2 shows that the dimples are formed over the entire central portions of the sheets within the margins of the edges mentioned, as the normal plane of the sheet is on the horizontal lines shown to extend across the exchanger and also on the junction of the crimped sheet edges. No portions parallel to this horizontal plane exist in the central sections of the sheets except for the crests as mentioned. Of course, the height and size of the dimples determines the flow area and surface, and the entire central area of the sheet is dimpled; that is, there is no horizontal portion of sheet between the dimples, and only the crests of the dimples are flat or horizontal in the central or intermediate area of the sheet. The degree of offset of the sheet edges out of the normal plane of the sheet is proportioned according. to the flow area provided within the pass.. The sheets are of material generally in thickness of .002 to .010 inch, and are preferably of stainless steel. ,It will also be understood that all four sides or edges of each sheet 20, 21, 22, and 23 are bonded either to another sheet or to the plates and 11, as with the sheets 20 and 23. The plurality of cross-flow passes is thus formed, with the protrusions providing the sheet spacing and strength without the requirement of internal fins or other structure.

A simple and thus one preferred form of the corner cut-out of the sheets is as shown in Figs. 6, 7, 8 and 9. In these showings, the sheets 20 through 23 are cut-out to each have a parallel sided slot defined by sheet edges 33 which exists at each corner of the exchanger and the slot or opening extends from the sheet corners to the interior, as shown. Then the corner pieces will nest in the slots with only the straight and flat or parallelsided portion 17 of the corner piece 13 in the slot 33, as in Figs. 6 and 8, the inner end of a straight corner piece 34 disposed in the shit or cut-out 33, as in Fig. 9. The angle portion of the corner piece is thus available along with the edges of the plates 10 and 11, for welding to connections or duct work 36. Also, the outer end of the piece 34 can be split and flared as at 37 to provide two branches for attachment to connections or duct work 38 which can be welded to the corner pieces. In this instance, the plates 10 and 11 have cut-outs corresponding to the flare at 37 Inall instances, the sheets and the plates at their ent-outs are bonded to the corner pieces. Also, the depth of the cut-outs is beyond the extent of the folds in the edges of the sheets to allow for reverse folding of adjacent corners of each sheet. The cut-outs are thus defined by sheet edges diametrically oppositely faced toward each other surrounded on three sides in the sheets. Therefore, the bond of the corner piece with the sheets is not likely to be broken since the sheets themselves support the piece in all directions except, in the direction of the stern of the Y.

While specific embodiments or this invention have been shown and described, it should be obvious that certain changes could be made therein, and the invention sheiild, therefore, be limited only by the scope of the appended claims.

What is claimed is:

1. In a heat exchanger ofthe type consisting of layers of rectangular sheets bonded together at their edges and 1 adaptable to be attached to headers or the like, the invention comprising said sheets each having an aligned opening extending transversely therethrough at the corners of said sheets, the bouridaries on opposite sides of said aligned openings being defined by sheet edges diametrically oppositely disposed to face each other and present a substantially enclosed opening in each of said sheets, and a corner piece disposed in said opening and including a first portion having the shape of and being fluid-tightly bonded to said boundaries and being of a length to extend across the layers of said sheetsand ineluding a second portion disposed exteriorly of and away from said sheets and said second portion presenting a surface for attaching a header thereto.

2. In a heat exchanger 'of the type consisting of layers of rectangular sheets bonded together at their edges and adaptable to be attached to headers or the like, the in vention comprising said sheets each having an aligned opening extending transversely therethrough at the corners of said sheets, said opening being defined by parallel edges on said sheets extending into said sheets to present a rectangularly shaped opening, and a Y-shaped corner piece fluid-tightly bonded to said sheets and extending thereacross with the lower stem portion of said Y-shaped corner piece being of the shape of said opening and disposed in said opening and being fluid-tightly bonded to the entire length of the edges of said sheets defining said opening, andwith the remaining portions of said Y-shaped corner piece extending outwardly from said sheets in free ends, spaced therefrom to present surfaces for attaching a header thereto.

7 3. In a heat exchanger of the type e'ohsistihg of a ers of rectangular sheets bonded together at their ends and adaptable to be attached to headers or' the like, the invention comprising said sheets each having an aligned opening extending transversely therethrough at the corners of said sheets, said aligned openings on said sheets being defined by diametrically oppositely faced edges disposed to face each other, a corner piece disposed in said opening and including a first portion fluid-tightly bonded to the complete lengths of said diametrically oppositely faced edges and being of a length to extend across the layers of said sheets and including a second portion disposed exteriorly of said sheets and said first portion for presenting a surface for attaching a header thereto, said sheets being dimpled over their entire inferior surfaces in fiat circular crests disposed in abutment with the crests on the adjacent sheets and being bonded thereto, said ends of said sheets being bonded to said ends of adjacent said sheets in alternate pattei'ns for providing one fluid pass through said exchanger between two said corner pieces thereof and for providing another and separate fluid pass through said exchanger between one of said two corner pieces and a third said corner piece.

4. A prime surface heat exchanger of the cross-flow type for conducting one fluid therethrough in one direction and another fluid therethrough in another direction, comprising a plurality of dimpled sheets disposed in layers with the central area of each of said sheets being entirely covered with protrusions alternately disposed on opposite sides of each of said sheets, said protrusions on each of said sheets being disposed to both sides of the original plane of each of said sheets and terminating in flat crests constituting a first portion of said sheets disposed parallel to said original plane and with the entire remainder of said central area of said sheets constituting a second portion of said sheets interconnecting 'said crests and being disposed oblique to said original plane and.

intermediate said crests, said crests on opposite sides of said sheets being bonded to said crests on adjacent ones of said sheets, said sheets each having an aligned opening extending transversely therethrough at the corners of said sheets, said opening being defined by parallel edges on said sheets extending into said sheets to present a rectangularly shaped opening, and a Y-shaped corner piece fluid-tightly bonded to said sheets and extending thereacross with the lower stem portion of said Y-shaped corner piece being of the shape of said opening and disposed in said opening and being fluid-tightly bonded to the entire length of the edges of said sheets defining said opening, and with the remaining portions of said Y-shaped corner piece extending outwardly from said sheets in free ends spaced therefrom to present surfaces for attaching a header thereto.

References Cited in the file of this patent UNITED STATES PATENTS Kucher et al Aug. 1, Simpson Dec. 14, Pitt Feb. 22, Simpelaar Jan. 30, Collins May 6,

FOREIGN PATENTS Norway July 20, Germany June 23, France July 16, 

